Process for the manufacture of aluminum halide catalysts



Patented Jan. 16, 1951 PROCESSFOR THE MANUFACTURE OF ALUMINUM HALIDECATALYSTS Thomas H. Whaley, Jr., Bartlesville, Okla., assignor toPhillips Petroleum Company, a corporation of Delaware No Drawing.Application August 24, 1945,

Serial No. 612,540

1 '7 Claims. The present invention relates to an improved process forthe manufacture of catalysts for use in hydrocarbon conversionprocesses.

In many hydrocarbon conversion processes, such as, for example,cracking, isomerization,

alkylation, polymerization, Friedel and Crafts reactions, etc.,catalysts are employed to accelerate the rate of reaction. Of thecatalysts commonly employed in these reactions, aluminum chloride is ofincreasing importance. Aluminum chloride as generally used is in theform of a fine powder, which may be suspended in the hydrocarbons toform a slurry, or in the form of large lumps which are homogeneous orsupported on a carrier material. Solid aluminum chloride is sometimesadmixed with or deposited on Raschig rings or other inert forms toobtain a catalyst bed having sufiicient permeability to allow flow ofhydrocarbon liquids or vapors therethrough. The lumps of solid aluminumchloride are more or less porous and are subject to coalescence orfusion into a compact mass of relatively poor catalytic activity. Duringthe conversion process aluminum chloride forms a Sludge or hydrocarboncomplex. As the catalyst in admixture with inert solid material isconverted to sludge, the sludge is deposited on the inert material,hindering the action of the catalyst. Powdered aluminum chloride is notwell adapted for use in a stationary catalyst. bed since a stationarymass of the powdered catalyst is relatively impervious and is subject tocaking into a solid mass. suspension in the hydrocarbon reactants aserious corrosion and erosion problem is -encou'ntered. The aluminumchloride suspension in motion literally cuts the apparatus to pieces;

The cor-,

resulting in very short equipment life. rosion and erosion is especiallysevere on agitators, pumps, valves and piping handling the suspension orslurry and on the catalyst cases at points of contact with movingaluminum chloride. Some difficulty is encountered also inretaining thepowdered aluminum halide in suspension, the powder tending to collectand agglomerate in the equipment at places where there is insufficientflow or agitation to keep the particles separate and in suspension andto form cakes or lumps which are not readily resus pended.

It has been proposed heretofore to provide an active bed of aluminumchloride catalyst by subliming aluminum chloride upon a porous. inertcarrier. While the catalyst prepared in this manner is sometimessatisfactory when first When used. as a put in use, it is subject tosome extent to the objections set forth in regard to the use of aluminumchloride deposited on Raschig rings. In many cases, the catalysts formedin this manner soon show inferior activity due to the absorption of thesludge, formed particularly when aluminum chloride is used, on theporous catalyst carrier. A further disadvantage of these catalystsarises from the fact that some porous carriers, otherwise suited ascatalyst carriers,

promote undesirable reactions or adversely alfect I the desiredhydrocarbon conversion.

In my copending patent application, Serial No. 460,861, filed October 5,1942, of which this is a continuation-impart,and which issued October 9,1945 as Patent No. 2,386,524, is disclosed an aluminum halide catalystin the form of fibres or threads. The present invention is directed tothe preparation of compact solid masses of aluminum halides, preferablyin the form of drops, pellets or beads having low surfacevolume ratios.The drops, pellets or beads producedin accordance with this invention,as opposed to conventional lump forms of aluminum halide, aresubstantially non-porous and of a form approaching minimum surface areaper unit volume for any given size particle. Advantages ofthe catalystproduced by my process arise from the fact that the particle structureis such that it is very resistant to crushing, hav- -ing high mechanicalstrength, and may be transferred in the equipment without seriouserosive action. The catalyst produced by my process may be used instationary beds or in moving beds with many advantages over theconventional aluminum halide catalysts. When used in stationary beds,the catalyst allows free flow of reactants through the catalyst bedwithout substantial movement of the particles. Being in anextraordinarily dense form, the aluminum halide particles do not readilycrush to form objectionable powdered aluminum halide. Also the drops,beads or pellets, when kept in anhydrous condition, are free flowingand, possessing extraordinarily high density and mechanical stability,are particularly useful for moving catalyst beds. Heretofore, movingaluminum halide catalysts have been possible only by use of powderedcatalyst, the disadvantages of which are discussed hereinabove. Animportant contribution to the art of catalytic conversion ofhydrocarbons with aluminum halide catalysts is made, therefore, by thepresent invention, which provides a solid aluminum halide catalysthaving high density and mechanical stability capable of free flowwithout serious erosion, and capable of self support under many reactionconditions. The catalyst produced by my process is, therefore, superiorin many respects to the lump or powdered forms used heretofore.

In addition to the advantages of! the catalyst produced by my process incertain conversion processes, it possesses advantages in thetransportation of aluminum halides from'the place of manufacture to thepoint ofuse and. in handling prior to use. The drops, pellets or beadsof aluminum halide may be made in accordance with this invention andshipped in drums or other suitable shipping containers to=the hydro--carbon conversion plant where they may be converted to one of theconventional forms. prior to use in the process. For example, thedrops}. pellets or beads may be vaporized and the vapors deposited on aparticulate carrier material, as alumina, for use in conventionalmanner. The drop, pellet or bead form is particularly useful. in thisinstance in the transportation and ham dling of the aluminum halideprior to use. There is little tendency for the drops, pellets or beadsin anhydrous form to disintegrate or" cake during transportation. Thefree flowing quality of the catalyst makes it particularly easy to emptythe catalyst containersat the point of use and to transfer the catalystto the process equipment.

Other objects and advantages will be evident from the following detaileddisclosure.

The aluminum halides are aluminum fluoride, M. P. 1040 0.; aluminumbromide, M. P. 97.5 0.; aluminum iodide, M. P'. 191 C.'; and aluminumchloride, which sublimes at 178 C. at atmospheric pressure but hasamelting point of about 194 C. at 5.2 atmospheres pressure. Of thesehalides, the chloride, bromide, and iodide are preferred as catalyticmaterials-for use in accordance with my invention.

In practicing the process of my invention, the aluminum halide isrendered plastic, preferably by heating to a temperature in the regionof its melting point or above under sufiicient pressure to substantiallypreclude vaporization of the aluminum halide.

The plastic or molten aluminum halide is then formed into small compactmasses having a low ratio of external surface to volume for a givenparticle size, referred to herein as pellets, of small diameter to yielda product similar in a'p'-- pearance to glass beads. These pellets mayrange from very small diameter, e; g., 0.1 inch-or smaller to a diameterof about 0.5 inch, or larger; preferably the pellets have-a diameter of-0.2' to 0.4 inch. In general, the pellets may be formed in the manner ofmanufacture of glass beads, lead shot, or pharmaceutical pills, certainprecautions being necessary as will be described more fully hereinafter.

Because of the corrosive properties of molten aluminum chloride, thevessel in which it is heated or fused should be made of or lined with amaterial resistant to corrosion bythe aluminum chloride. Amongthematerials of construction which are generally suitable are alloys ofiron containing high percentages of silicon or nickel; certain alloys ofnickel, copper, and" chromium, as well as other alloys containing highpercentages of one or more of these metals; alloys of tungsten; certaincast bronzes; and deoxidized copper, preferably containing a smallpercentage of phosphorus. Most of these materials are preferablyfabricated by casting to thedesired shape. Corrosion-resistant liningsof glass, resins, cement of highly siliceous material, tungsten,alundum, tungsten carbide, etc. may be used. Since the temperaturesrequired to plasticize the preferred halides (the chloride, bromide, andiodide) are relatively moderate, the temperature resistances of thematerials are not critical limiting factors in their selection. Moderatepressure is maintained on the molten aluminum halide to preventexcessive vaporization or subliming when heating the halide to plasticor molten state. A pressure of 50 to 150 pounds per square inch gauge isgenerally sufficient inv the case of aluminum chloride; the aluminumbromide and iodide may be worked at substantially atmospheric pressurebut preferably are maintained under superatmospheric pressure up toabout pounds per square inch gauge.

As a specific example of a method of preparing an aluminum halidein theform of pellets in accordance with my invention, anhydrous aluminumchloride is heated in a closed vessel to a temperature-of 200 C. in anatmosphere of dry nitrogen. The molten aluminum chloride is admitted toa heated extrusion device of conventional design, wherein mechanicalpressure is applied to force the plastic aluminum chloride through anorifice of approximately the diameter desired for the finished pellet,equipped with means for shearing, breaking, or interrupting the flow ofaluminum chloride to form segmental particles having a lengthapproximately equal to the diameter of the extruded aluminum chloride.Upon heating to 200 C. under pressure, aluminum chloride attains a veryviscous fluid state which may be handled as' a plastic. When extruded inconventional plastic extrusion apparatus, the extruded portion tends topuff up to form a very porous mass. The puffing tendency is overcome inthe present process by the use of pressure on the plastic mass in excessof the vapor pressure of aluminum chloride during the period" requiredto cool the aluminum chloride below'its vaporization temperature (178C.) at atmospheric pressure. This produces an extraordinarily denseproduct which retains its dense properties at ordinary temperatures. Thealuminum chloride pellets produced as described above are dischargedinto a cooling chamber in which cooled nitrogen at a pressure of about'75 pounds per' square inch gauge is continuously circulated.

Th'e'orifice of the extrusion device is particularly' subject to theerosive action of the molten aluminum chloride and is suitably formed oftungsten. carbide or alundum, which materials are. extremely resistantto erosion. The pellets formed by the extrusion device are rapidlycooled to solid condition by the relatively cold inert gas maintainedunder a pressure in excess of the. vapor pressure of the aluminumchloride. The pressure in the cooling chamber precludes sublimation ofthe aluminum chloride and expansion ofthe plastic aluminum chloride toany appreciable extent. A compact pellet having good. structuralproperties is thereby formed.

Hydrogen chloride may be employed as the inert gasandma'y be in somecases the preferred inert gas for cooling, the aluminum chloride pelletssince it acts asian activator for the catalyst. Similarly, the otherhydrogen halides may be preferred as atmospheres in the manufacture ofthe aluminum bromide and aluminum iodide catalysts. While thesegases maynot be, strictly from the edges of the plate.

speaking, inert in the chemical sense, they do not, when properlycorrelated with the aluminum halide being treated, have a deleteriouselfect on the catalyst. Other gases which are not harmful to thecatalyst may be employed, for example, hydrocarbon vapors, chlorine,hydrogen, and the rare gases. The gases brought into contact are in anycase anhydrous and free from oxygen or other deleterious contaminants.gas in the molten aluminum chloride should be avoided as much aspossible as the dissolved gases reduce the density of the pellet and maycause undesirable bubbles or pores in the pellet which seriously reduceits mechanical strength and stability. The expedient of cooling thepellet under pressure minimizes the tendency of bubble formation afterthe pellet is formed.

Aluminum bromide and aluminum iodide, both of which may be fused atatmospheric pressure, present less difficulty in pellet formation thandoes aluminum chloride and less tendency for the pellet to expand afterformation.

The pellets of aluminum halide may be manufactured by the formation ofdrops of the aluminum halide and cooling of the drops to pellets in adry, non-deleterious atmosphere. The fluid aluminum halide may beallowed to escape from the retort, i. e., the vessel in which it isheated, or some suitable associated apparatus, into an inert atmospherethrough openings which produce drops. Apparatus of this nature hasbeenused in the formation of lead shot. The molten aluminum halide maybe poured onto a heated foraminous plate having openings therethrough,preferably somewhat smaller at the outlet than at the inlet. The actionof gravity upon the molten aluminum halide causes drop formation at theoutlet side of the openings. The drop formation may, of course, beinduced by or result from the action of suitable mechanical means. Thedrops of aluminum chloride may be subjected during formation, as well asafter formation, to the cooling action of a stream of substantially dryinert gas. Inert liquids may also be employed for cooling of thepellets, particularly he halogenated hydrocarbons. The inert gas orliquid employed may be circulated in such a manner as to aid in thepellet formation; when using gas, the circulation is preferablycountercurrent to the direction of travel of. the drops of plasticaluminum halide; with liquid, agitation of the liquid coolant issufficient to aid in the formation of substantially spherical pelletsfrom the plastic drops. Suflicient pressure is maintained in the coolingchamber to insure formationof a compact pellet. The pressure somaintained is in excess of the vapor pressureof the aluminum halide atthe temperature employed in the formation of the plastic aluminum halidepellets.

Another method which may be employed in forming the pellets involves theuse of centrifugal force to cause the fluid aluminum halide to formplastic drops which are cooled in an inert cooling atmosphere topellets. For example, the molten aluminum'halide may be thrown by theaction of centrifugal force from the periphery of a rotating circulardisk in the form of small drops. This principle is relatively well knownSolution of and needs very little description. The aluminum halide isrevolved at a relatively rapid rate on a circular plate. Small particlesbreak away from the revolving mass and are thrown outwardly Theparticles assume a substantially spherical shape; size may be the speedof rotation. The particles are given a rolling action by the plate asthey leave the revolving mass resulting in the formation of sphericalplastic particles, which, upon cooling result in dense pellets.Apparatus of this type may be used to produce pellets suitable for useas catalysts in accordance with my invention.

The pellets of aluminum halide may be produced in machines similar tothose used for the manufacture of catalyst pellets of silica gel orsynthetic alumina. In the manufacture of pellets by this means, thematerial to be pelleted is charged in small predetermined quantitiesinto molds to which mechanical pressure is applied to form the pellet.The manufacture of aluminum halide pellets, particularly aluminumchloride pellets, by this method require conditions not employed in themanufacture of conventional catalyst pellets, First, the aluminum halidemust be rendered plastic; conventional pellets from other catalyticmaterials are formed merely by compression of powders. Second, apressure higher than the vapor pressure must be maintained 0n the pelletuntil it has cooled below the vaporization temperature (178 C. foraluminum chloride); conventional pellets made from other catalyticmaterials require no cooling and pressure is not required after catalystformation. With apparatus of this nature, the aluminum halide may becharged in plastic state to the mold in required quantities. The molditself may be cooled or the pellets may be discharged from the mold intoa cooling atmosphere. Sufficient pressure is maintained during thecooling period to prevent vaporization. Alternatively, powdered aluminumhalide may be charged to heated molds which render the aluminum halideplastic during the molding operation. The pellets thus formed are cooledin the mold or in an inert atmosphere. The pellets may also be molded insuitable molds in an inert atmosphere under sufficient pressure tosubstantially preventvaporization, without the use of mechanicalpressure. Two types of molding machines, using mechanical pressure,which may be satisfactorily employed are the ram type and the rollertype. In the ram type, the aluminum halide is placed in the mold andpressure applied with a rod or ram which carries a complementary portionof the mold. In the roller type, the plastic mass of aluminum halide isfed onto two cooperating, counter-rotating rollers which are pressedtightly together at their points of contact with complementary recessesin each to receive and mold the aluminum halide into pellets of thedesired size and. shape.

The aluminum halide catalyst in the pellet form produced by my processmay be advantageously used in hydrocarbon conversion processes in whichthe aluminum halide may be maintained normally in solid form. Thecatalyst is capable of self-support when used under conditions oftemperature below the softening or fusion point. In these operations acatalyst chamber is provided with means for support of the catalystmass, either, in its entirety or in sections. The catalyst chambers aregenerally provided with a foraminous plate to support the solid catalystmass and may be provided atintervals with foraminous partitions whichretain the catalyst while allowing free passage of the hydrocarbonstherethrough. The catalyst case is filled with the pellet catalyst andprovision may be made .for removal of particles of the catalyst carriedin the hydrocarbons as the pellets disintegrate with use. Fresh catalystis added as needed to replenish the catalyst bed, the fresh-catalystbeing introduced preferably at thei hydrocarbon outlet. The freshcatalytic material thereby acts as a filtering agent for small catalystparticles, retaining them in the catalyst zone until spent. The freshcatalyst may be supplied to the-catalyst chamber continuously orintermittently. Preferably the flow of hydrocarbons through the catalystbed is upward through thecatalyst pellets. This allows any sludgeformedin the reactionto separate from the catalystat thepoint at whichthe sludg'e formation is generally greatest and prevents its depositionon the catalyst'in the-remainder of the catalyst bed; Fresh pelletsadded to the top of the bed are of full size, with particle sizedecreasing from the top to the bottom of the beddue to size reductionwith use. Thevery small pellets at the bottom of the'bed may be drawnoff with the sludge.

The pellets of aluminum halide catalyst produced by my process may alsobe used in a moving catalyst bed. Fresh catalyst may be introducedcontinuously or intermittently to the top of the catalyst bed and usedcatalyst continuously or intermittently removed from the bottom of thebed. The shape and density of the pellets are conducive to free flow ofthe catalyst. The hydrocarbon flow may be in either direction throughthe catalyst bed. The used catalyst and sludge are preferably removedtogether from the bottom of the catalyst bed. The sludge may then beseparated from the catalyst, as by washing with aninert hydrocarbon, andthe clean catalyst recycled to the catal-yst'zone, preferably at a pointintermediate the ends of the catalyst bed.

In some catalytic processe in which the aluminum halides are used ascatalysts, the aluminum halide is dissolved in the hydrocarbonreactants; in others the hydrocarbon is passed over aluminum halideprior to introduction of the hydrocarbon to the catalyst chamber tosaturate thehydrocarbon with the aluminum halide. The catalytic materialproduced by my process may be advantageously used by either of theseprocedures. The pelleted aluminum halide used in this manner possessesseveral advantages over the lump or powdered form aspreviously pointedout.

Asa less desirable modificationof the'method of use of the catalyticmaterials produced by my process, the pelletsmay be suspended in thehydrocarbon stream in the catalytic reaction zone in much the samemanner as powdered aluminum halides. While there is still the erosionproblem mentioned in discussion of the powdered halide, the erosionisless severetha-n with the powdered halide. The smooth surfaces of thedense pellets are an important factor in'the lessening of the erosionproblem. The physical form of the aluminum halide pellets is believed'tohave a direct bearing upon the'reduction of corrosion obtaining when thepellets are employed in suspension.

I claim:

1. A process for manufacturing smooth, hard, dense catalytic pellets ofaluminum halide which comprises heating aluminum halide under asuperatmospheric pressure in excess of the vapor pressure of said halideand up to 150 p. s. i. g; so as to form a fluid'mass, thereafter formingsaid fluid mass into pellets between 0.1 and 0.5 inch in diameter whileunder said pressure, and cooling said pellets to a temperature below thesoftenin'g point of said halide at atmospheric pressure whileunder saidsuperatmospheric pressure so as to obtain said smooth; hard,densealu'minum halide pellets.

2. A process for manufacturing smooth, hard, dense catalytic pellets ofaluminum chloride which comprises heating aluminum chloride under asuperatmospheric pressure in excess of the vapor pressure of saidchloride and up to 150 p. s. i. g. so as to form a fluid mass,thereafter forming said fluid mass into pellets while under saidpressure, and cooling said pellets to a temperature below the'softeningpoint of said chloride at atmospheric pressure while undersaidsuperatmospheric pressure so as to obtain said smooth, hard, densealuminum chloride pellets.

3. A- process for manufacturing smooth, hard, dense catalytic pellets ofaluminum chloride which comprises heating aluminum chloride to themolten state; forming the molten aluminum chloride into'spheres rangingin diameter from 6.1 to 0.5 inch; cooling said spheres in an inertgaseous atmosphere; and maintaining said aluminum chlorideunder' asuperatmospheric pressure 6 in excess of the vapor pressure thereof andup to 150" p. s; i. g. during the preceding steps so as to form smooth,hard, dense, spherical pellets.

4. The process of 'claim 2 in which said pellets are cooled in anambientinert with respect to aluminum chloride.

5'. The process of claim 2 in which said pellets are cooled in nitrogen.

61 The process of claim 2 in which said pellets are cooled in liquidhalogenated hydrocarbon.

7L The process of claim 2 in which said pellets are formed byextrusion"and division ofthe extrudate into shortlengths.

THOMAS H. WHALEY. JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,146,363 Statham July 13, 19151,680,807 Schultze Aug. 14, 1928 2,283,174 Bates et a1. May 19, 19422,287,029 Dowd'ell June 23, 1942 2,295,977 Thomas et a1 Sept. 15, 19422,380,703 Montgomery et a1. July 31, 1945 2,386,524 Whaley Oct. 9, 19452,398,557 Reading Apr. 16, 1946

1. A PROCESS FOR MANUFACTURING SMOOTH, HARD, DENSE CATALYTIC PELLETS OFALUMINUM HALIDE WHICH COMPRISES HEATING ALUMINUM HALIDE UNDER ASUPERATMOSPHERIC PRESSURE IN EXCESS OF THE VAPOR PRESSURE OF SAID HALIDEAND UP TO 150 P.S.I.G. SO AS TO FORM A FLUID MASS, THEREAFTER FORMINGSAID FLUID MASS INTO PELLETS BETWEEN 0.1 AND 0.5 INCH IN DIAMETER WHILEUNDER SAID PRESSUER, AND COOLING SAID PELLET TO A TEMPERATURE BELOW THESOFTENING POINT OF SAID HALIDE AT ATMOSPHERIC PRESSURE WHILE UNDER SAIDSUPERATMOSPHERIC PRESSRE SO AS TO OBTAIN SAID SMOOTH, HARD, DENSEALUMINUM HALIDE PELLETS.